The present invention relates to a plain bearing comprising two plain bearing halves which form a cylindrical shape in combination and are fixed in a housing and in each of which an oil groove is formed on an inner circumferential surface along a circumferential direction and crush relieves are formed at both ends of the inner circumferential surface in the circumferential direction.
Conventionally, in plain bearings that support a rotating shaft such as a crankshaft for internal combustion engines, plain bearings comprising two plain bearing halves which form a cylindrical shape in combination are used. They have structure in which lubrication oil is supplied between the plain bearing and the rotating shaft by oil grooves formed on an inner circumferential surface of the plain bearing halves in a circumferential direction to form an oil film therebetween.
In such plain bearings, in order to prevent the lubrication oil in the oil grooves from leaking from vicinities of joints of the plain bearing halves, it has been proposed to locate ends of the oil grooves at predetermined positions spaced from ends of the plain bearing halves instead of providing the oil grooves circumferentially over the entire plain bearing halves, thereby preventing the lubrication oil in the oil grooves from entering the joints of plain bearing halves (for example, see JP-Y2-61-573).
On the other hand, in the case of the plain bearing comprising plain bearing halves described above, when plain bearing halves are mounted in the housing, there are some cases where misalignment is generated at joints of ends of plain bearing halves, or deformation is caused in the vicinity of the joints of the ends of the plain bearing halves if crush height is too high. Such misalignment or deformation at the joints possibly produces a bulge in a radial and inward direction and the bulge comes into local contact with a shaft.
Therefore, it has been proposed to form crush relieves at both ends of the inner circumferential surfaces of the plain bearing halves in the circumferential direction, thereby preventing local contact between the ends of the plain bearing halves and the shaft. In such plain bearings in which crush relieves are formed, there is a problem that the lubrication oil supplied to the oil grooves flow into the crush relieves to leak out from the crush relieves in an axial direction, so that oil pressure in a lubricating system is lowered.
By the way, the plain bearing disclosed in JP-Y2-61-573 is not formed with crush relieves and so free from the problem that leakage of a lubrication oil due to the provision of the crush relieves results a drop in oil pressure in the lubricating system, but involves a problem that local contacts are resulted between ends of plain bearing halves and the shaft.
In view of the above circumstances, the invention has been thought of and has its object to provide a plain bearing which has crush relieves and can prevent reduction in oil pressure in a lubricating system.